The sociology of religion concerns the role of religion in society; the practices, historical backgrounds, developments and universal themes of religion in society.[1] There is particular emphasis on the recurring role of religion in all societies and throughout recorded history. The sociology of religion is distinguished from the philosophy of religion in that it does not set out to assess the validity of religious beliefs, though the process of comparing multiple conflicting dogmas may require what Peter L. Berger has described as inherent "methodological atheism".[2] Whereas the sociology of religion broadly differs to theology in assuming the invalidity of the supernatural, theorists tend to acknowledge socio-cultural reification of religious practise.

According to one common typology among sociologists, religious groups are classified as ecclesias, denominations, sects, or cults (now more commonly referred to in scholarship as NRMs). Note that sociologists give these words precise definitions which are different from how they are commonly used. Particularly the words 'cult' and 'sect' are used free from negative connotations by sociologists, even though the popular use of these words is often pejorative.

Durkheim, Marx, and Weber had very complex and developed theories about the nature and effects of religion. Durkheim and Weber specifically are often difficult to understand, especially in light of the lack of context and examples in their primary texts. Religion was considered to be an extremely important social variable in the work of all three:

Despite his later influence, Karl Marx did not view his work as an ethical or ideological response to nineteenth-century capitalism (as most later commentators have). His efforts were, in his mind, based solely on what can be called applied science. Marx saw himself as doing morally-neutral sociology and economic theory for the sake of human development. As Christiano states, "Marx did not believe in science for science’s sake…he believed that he was also advancing a theory that would…be a useful tool…[in] effecting a revolutionary upheaval of the capitalist system in favor of socialism." (124) As such, the crux of his arguments was that humans are best guided by reason. Religion, Marx held, was a significant hindrance to reason, inherently masking the truth and misguiding followers. As we will later see, Marx viewed social alienation as the heart of social inequality. The antithesis to this alienation is freedom. Thus, to propagate freedom means to present individuals with the truth and give them a choice to accept or deny it. In this, "Marx never suggested that religion ought to be prohibited." (Christiano 126)

Central to Marx's theories was the oppressive economic situation in which he dwelt. With the rise of European industrialism, Marx and his colleague Friedrich Engels witnessed and responded to the growth of what he called "surplus value." Marx’s view of capitalism saw rich capitalists getting richer and their workers getting poorer (the gap, the exploitation, was the "surplus value"). Not only were workers getting exploited, but in the process they were being further detached from the products they helped create. By simply selling their work for wages, "workers simultaneously lose connection with the object of labor and become objects themselves. Workers are devalued to the level of a commodity – a thing…" (Ibid 125) From this objectification comes alienation. The common worker is told he or she is a replaceable tool, alienated to the point of extreme discontent. Here, in Marx’s eyes, religion enters. Capitalism utilises our tendency towards religion as a tool or ideological state apparatus to justify this alienation. Christianity teaches that those who gather up riches and power in this life will almost certainly not be rewarded in the next ("it is harder for a rich man to enter the Kingdom of Heaven than it is for a camel to pass through the eye of a needle...") while those who suffer oppression and poverty in this life, while cultivating their spiritual wealth, will be rewarded in the Kingdom of God. Thus Marx's famous line - "religion is the opium of the people", as it soothes them and dulls their senses to the pain of oppression.

Émile Durkheim placed himself in the positivist tradition, meaning that he thought of his study of society as dispassionate and scientific. He was deeply interested in the problem of what held complex modern societies together. Religion, he argued, was an expression of social cohesion.

In the fieldwork that led to his famous Elementary Forms of Religious Life, Durkheim, a secular Frenchman, looked at anthropological data of Indigenous Australians. His underlying interest was to understand the basic forms of religious life for all societies. In Elementary Forms, Durkheim argues that the totems the aborigines venerate are actually expressions of their own conceptions of society itself. This is true not only for the aborigines, he argues, but for all societies.

Religion, for Durkheim, is not "imaginary," although he does deprive it of what many believers find essential. Religion is very real; it is an expression of society itself, and indeed, there is no society that does not have religion. We perceive as individuals a force greater than ourselves, which is our social life, and give that perception a supernatural face. We then express ourselves religiously in groups, which for Durkheim makes the symbolic power greater. Religion is an expression of our collective consciousness, which is the fusion of all of our individual consciousnesses, which then creates a reality of its own.

It follows, then, that less complex societies, such as the Australian aborigines, have less complex religious systems, involving totems associated with particular clans. The more complex the society, the more complex the religious system. As societies come in contact with other societies, there is a tendency for religious systems to emphasize universalism to a greater and greater extent. However, as the division of labor makes the individual seem more important (a subject that Durkheim treats extensively in his famous Division of Labor in Society), religious systems increasingly focus on individual salvation and conscience.

Durkheim's definition of religion, from Elementary Forms, is as follows: "A religion is a unified system of beliefs and practices relative to sacred things, that is to say, things set apart and forbidden – beliefs and practices which unite into one single moral community called a Church, all those who adhere to them." (Marx, introduction) This is a functional definition of religion, meaning that it explains what religion does in social life: essentially, it unites societies. Durkheim defined religion as a clear distinction between the sacred and the profane, in effect this can be paralleled with the distinction between God and humans.

In his sociology, Weber uses the German term "Verstehen" to describe his method of interpretation of the intention and context of human action. Weber is not a positivist – in the sense that he does not believe we can find out "facts" in sociology that can be causally linked. Although he believes some generalized statements about social life can be made, he is not interested in hard positivist claims, but instead in linkages and sequences, in historical narratives and particular cases.

Weber argues for making sense of religious action on its own terms. A religious group or individual is influenced by all kinds of things, he says, but if they claim to be acting in the name of religion, we should attempt to understand their perspective on religious grounds first. Weber gives religion credit for shaping a person's image of the world, and this image of the world can affect their view of their interests, and ultimately how they decide to take action.

For Weber, religion is best understood as it responds to the human need for theodicy and soteriology. Human beings are troubled, he says, with the question of theodicy – the question of how the extraordinary power of a divine god may be reconciled with the imperfection of the world that he has created and rules over. People need to know, for example, why there is undeserved good fortune and suffering in the world. Religion offers people soteriological answers, or answers that provide opportunities for salvation – relief from suffering, and reassuring meaning. The pursuit of salvation, like the pursuit of wealth, becomes a part of human motivation.

In The Protestant Ethic, Weber argues that capitalism arose in Europe in part because of how the belief in predestination was interpreted by everyday English Puritans. Puritan theology was based on the Calvinist notion that not everyone would be saved; there was only a specific number of the elect who would avoid damnation, and this was based sheerly on God's predetermined will and not on any action you could perform in this life. Official doctrine held that one could not ever really know whether one was among the elect.

Practically, Weber noted, this was difficult psychologically: people were (understandably) anxious to know whether they would be eternally damned or not. Thus Puritan leaders began assuring members that if they began doing well financially in their businesses, this would be one unofficial sign they had God's approval and were among the saved – but only if they used the fruits of their labor well. This along with the rationalism implied by monotheism led to the development of rational bookkeeping and the calculated pursuit of financial success beyond what one needed simply to live – and this is the "spirit of capitalism." Over time, the habits associated with the spirit of capitalism lost their religious significance, and rational pursuit of profit became its own aim.

The Protestant Ethic thesis has been much critiqued, refined, and disputed, but is still a lively source of theoretical debate in sociology of religion. Weber also did considerable work in world religions, including Hinduism and Buddhism.

In relation to the processes of rationalisation associated with the development of modernity, it was predicted in the works of many classical sociologists that religion would decline. Despite the claims of many classical theorists and sociologists immediately after World War II, many contemporary theorists have critiqued secularisation thesis, arguing that religion has continued to play a vital role in the lives of individuals worldwide. In the United States, in particular, church attendance has remained relatively stable in the past 40 years. In Africa, the emergence of Christianity has occurred at a startling rate. While Africa could claim roughly 10 million Christians in 1900, recent estimates put that number closer to 200 million. The rise of Islam as a major world religion, especially its new-found influence in the West, is another significant development. Furthermore, arguments may be presented regarding the concept of civil religion and new world belief systems. In short, presupposed secularization as a decline in religiosity might seem to be a myth, depending on its definition and the definition of its scope. For instance, some sociologists have argued that steady church attendance and personal religious belief may coexist with a decline in the influence of religious authorities on social or political issues.